[RFC/RFT PATCH] net: stmmac: do not poke MAC_CTRL_REG twice on link up

[Da Xue]

On Fri, Aug 26, 2022 at 4:36 PM Heiner Kallweit <hkallweit1 at gmail.com> wrote:
>
> On 26.08.2022 17:45, Da Xue wrote:
> > Hi Heiner,
> >
> > I have been running with the patch reverted for about two weeks now
> > without issue but I have a modified u-boot with ethernet bringup
> > disabled.
> >
> > If u-boot brings up ethernet, all of the GXL boards with more than 1GB
> > memory experience various bugs. I had to bring the PHY initialization
> > patch into Linux proper:
> > https://github.com/libre-computer-project/libretech-linux/commit/1a4004c11877d4239b57b182da1ce69a81c0150c
> >
> Thanks for the follow-up. To be acceptable upstream I'm pretty sure that
> the maintainer is going to request replacing magic number 0x10110181
> with or'ing proper constants for the respective bits and fields.

Yes, it's a 32-bit field with a 32-bit value per the datasheet so a
full write will do without bits and xors. This was just a quick patch
from Duan. The patch as-is is not meant for upstream. I don't have any
ODROID-C2 to test GXBB so can someone please confirm it doesn't blow
anything up there? or maybe this should be a quirk for GXL only.

>
> > Hope this helps someone.
> >
> > Best,
> >
> > Da
> >
> > On Fri, Aug 26, 2022 at 5:51 AM Heiner Kallweit <hkallweit1 at gmail.com> wrote:
> >>
> >> On 07.07.2022 12:14, Jerome Brunet wrote:
> >>> For some reason, poking MAC_CTRL_REG a second time, even with the same
> >>> value, causes problem on a dwmac 3.70a.
> >>>
> >>> This problem happens on all the Amlogic SoCs, on link up, when the RMII
> >>> 10/100 internal interface is used. The problem does not happen on boards
> >>> using the external RGMII 10/100/1000 interface. Initially we suspected the
> >>> PHY to be the problem but after a lot of testing, the problem seems to be
> >>> coming from the MAC controller.
> >>>
> >>>> meson8b-dwmac c9410000.ethernet: IRQ eth_wake_irq not found
> >>>> meson8b-dwmac c9410000.ethernet: IRQ eth_lpi not found
> >>>> meson8b-dwmac c9410000.ethernet: PTP uses main clock
> >>>> meson8b-dwmac c9410000.ethernet: User ID: 0x11, Synopsys ID: 0x37
> >>>> meson8b-dwmac c9410000.ethernet:     DWMAC1000
> >>>> meson8b-dwmac c9410000.ethernet: DMA HW capability register supported
> >>>> meson8b-dwmac c9410000.ethernet: RX Checksum Offload Engine supported
> >>>> meson8b-dwmac c9410000.ethernet: COE Type 2
> >>>> meson8b-dwmac c9410000.ethernet: TX Checksum insertion supported
> >>>> meson8b-dwmac c9410000.ethernet: Wake-Up On Lan supported
> >>>> meson8b-dwmac c9410000.ethernet: Normal descriptors
> >>>> meson8b-dwmac c9410000.ethernet: Ring mode enabled
> >>>> meson8b-dwmac c9410000.ethernet: Enable RX Mitigation via HW Watchdog Timer
> >>>
> >>> The problem is not systematic. Its occurence is very random from 1/50 to
> >>> 1/2. It is fairly easy to detect by setting the kernel to boot over NFS and
> >>> possibly setting it to reboot automatically when reaching the prompt.
> >>>
> >>> When problem happens, the link is reported up by the PHY but no packet are
> >>> actually going out. DHCP requests eventually times out and the kernel reset
> >>> the interface. It may take several attempts but it will eventually work.
> >>>
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
> >>>> Sending DHCP requests ...... timed out!
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: Link is Down
> >>>> IP-Config: Retrying forever (NFS root)...
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: PHY [0.1:08] driver [Meson G12A Internal PHY] (irq=POLL)
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: No Safety Features support found
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: PTP not supported by HW
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: configuring for phy/rmii link mode
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
> >>>> Sending DHCP requests ...... timed out!
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: Link is Down
> >>>> IP-Config: Retrying forever (NFS root)...
> >>>> [...] 5 retries ...
> >>>> IP-Config: Retrying forever (NFS root)...
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: PHY [0.1:08] driver [Meson G12A Internal PHY] (irq=POLL)
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: No Safety Features support found
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: PTP not supported by HW
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: configuring for phy/rmii link mode
> >>>> meson8b-dwmac ff3f0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
> >>>> Sending DHCP requests ., OK
> >>>> IP-Config: Got DHCP answer from 10.1.1.1, my address is 10.1.3.229
> >>>
> >>> Of course the same problem happens when not using NFS and it fairly
> >>> difficult for IoT products to detect this situation and recover.
> >>>
> >>> The call to stmmac_mac_set() should be no-op in our case, the bits it sets
> >>> have already been set by an earlier call to stmmac_mac_set(). However
> >>> removing this call solves the problem. We have no idea why or what is the
> >>> actual problem.
> >>>
> >>> Even weirder, keeping the call to stmmac_mac_set() but inserting a
> >>> udelay(1) between writel() and stmmac_mac_set() solves the problem too.
> >>>
> >>> Suggested-by: Qi Duan <qi.duan at amlogic.com>
> >>> Signed-off-by: Jerome Brunet <jbrunet at baylibre.com>
> >>> ---
> >>>
> >>>  Hi,
> >>>
> >>>  There is no intention to get this patch merged as it is.
> >>>  It is sent with the hope to get a better understanding of the issue
> >>>  and more testing.
> >>>
> >>>  The discussion on this issue initially started on this thread
> >>>  https://lore.kernel.org/all/CAK4VdL3-BEBzgVXTMejrAmDjOorvoGDBZ14UFrDrKxVEMD2Zjg@mail.gmail.com/
> >>>
> >>>  The patches previously proposed in this thread have not solved the
> >>>  problem.
> >>>
> >>>  The line removed in this patch should be a no-op when it comes to the
> >>>  value of MAC_CTRL_REG. So the change should make not a difference but
> >>>  it does. Testing result have been very good so far so there must be an
> >>>  unexpected consequence on the HW. I hope that someone with more
> >>>  knowledge on this controller will be able to shine some light on this.
> >>>
> >>>  Cheers
> >>>  Jerome
> >>>
> >>>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 1 -
> >>>  1 file changed, 1 deletion(-)
> >>>
> >>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >>> index d1a7cf4567bc..3dca3cc61f39 100644
> >>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >>> @@ -1072,7 +1072,6 @@ static void stmmac_mac_link_up(struct phylink_config *config,
> >>>
> >>>       writel(ctrl, priv->ioaddr + MAC_CTRL_REG);
> >>>
> >>> -     stmmac_mac_set(priv, priv->ioaddr, true);
> >>>       if (phy && priv->dma_cap.eee) {
> >>>               priv->eee_active = phy_init_eee(phy, 1) >= 0;
> >>>               priv->eee_enabled = stmmac_eee_init(priv);
> >>
> >> Now that we have a3a57bf07de2 ("net: stmmac: work around sporadic tx issue on link-up")
> >> in linux-next and scheduled for stable:
> >>
> >> Jerome, can you confirm that after this commit the following is no longer needed?
> >> 2c87c6f9fbdd ("net: phy: meson-gxl: improve link-up behavior")
> >>
> >> Then I'd revert it, referencing the successor workaround / fix in stmmac.
>